The American law of freedom of expression developed largely in response to political and cultural progressive agitation. From the time of Justice Oliver Wendell Holmes' dissent in Abrams v. New York, the courts tacitly assumed that progressives' motives were sincere, that their goals were justified or at least fairly debatable, and that their occasional invocation of violent measures was not a serious threat to public order. The sanctity of free expression, both legally and culturally, is now increasingly being taken up by libertarians and reactionary populists on the right, to the discomfiture of progressives about what they call disinformation and hate speech. The change is driven by the fact that the structure of communication has changed in a way that abolishes the former distinction between speech and the press.

The First Amendment identifies freedom of speech and freedom of the press as two distinct liberties. That paralleled the English common-law distinction between two forms of defamation—oral slander and written libel. Libel was treated more severely in terms of both substantive liability and damages because the printed word was more permanent than ephemeral speech, more subject to exact reproduction, and able to reach a broader audience in both space and time.